Abstract
Key messageTree structure equations derived from pipe model theory (PMT) are well-suited to estimate biomass allocation in Scots pine (Pinus sylvestrisL.) and Norway spruce (Picea abies[L.] Karst.). However, age dependence of parameters should be accounted for when applying the equations.ContextPipe model theory-based (PMT-based) structure equations have been incorporated in many process-based models. However, more data concerning old-growth trees is needed to test the reliability and generality of the structure equations.AimsThis study (1) tested the age independence of the PMT-based structure equations and (2) provided general information about the stability of tree structure with age.MethodsA total of 162 Scots pine and 163 Norway spruce trees in four age groups were analysed to test the age effect on the parameters of structure equations using a linear mixed model. Biomass of stem, branch and foliage was estimated from destructive measurements, and with other tree dimensions, they were used to present the tree growth patterns.Results(1) Stem biomass proportion increased with age, while branch and foliage biomass proportion decreased; biomass allocation and most tree variables became steady after maturing. (2) PMT-based structure equations were well-suited to Scots pine and Norway spruce in all age groups; however, age dependence was detected in the parameters of these equations, except for the branch-related equations in Scots pine and stem form coefficient below the crown base in both species.ConclusionOur study (1) provides information applicable to predictions of growth and biomass allocation in old boreal stands and (2) suggests taking age effect into account when structure equations are implemented in forest growth models.
Highlights
The target of forest management and planning today has changed from a strong focus on timber production to a broader objective of sustainability, such as increased carbon sequestration and the maintenance of biodiversity (Lämås and Fries 1995; Cintas et al 2017; Triviño et al 2017)
(2) pipe model theory (PMT)-based structure equations were well-suited to Scots pine and Norway spruce in all age groups; age dependence was detected in the parameters of these equations, except for the branch-related equations in Scots pine and stem form coefficient below the crown base in both species. & Conclusion Our study (1) provides information applicable to predictions of growth and biomass allocation in old boreal stands and (2) suggests taking age effect into account when structure equations are implemented in forest growth models
The primary objectives of this study were (1) to provide, using this example, more general information about the growth patterns of tree structure with age; and (2) to test the age independence of the PMT-based structure equations in boreal Scots pine and Norway spruce with specific focus on old trees, and to modify the equations for age groups if required
Summary
The target of forest management and planning today has changed from a strong focus on timber production to a broader objective of sustainability, such as increased carbon sequestration and the maintenance of biodiversity (Lämås and Fries 1995; Cintas et al 2017; Triviño et al 2017). This places new demands on management-oriented forest models: in order to assess the emerging management methods, they need to be applicable to the new types of stand created by these alternative management strategies. Carbon allocation patterns in old-growth stands have become essential, as carbon allocation is considered an important factor in predicting forest growth (Purves and Pacala 2008; Ise et al 2010; Franklin et al 2012)
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